For a discharge surface treatment in which an electrode material is supplied to the surface of a treatment target member by generating a pulsating discharge across an inter-electrode gap, which is the clearance between a discharge surface treatment electrode and the treatment target member, and a coating made of the electrode material is formed on the surface of the treatment target member, as a circuit that generates a low-energy discharge, there is a capacitor circuit that causes the charge supplied from a DC power source to be stored in a capacitor provided between the DC power source and the inter-electrode gap. In this capacitor circuit, when the charging voltage of the capacitor becomes high, breakdown of the inter-electrode gap occurs and an electric discharge occurs; therefore, a discharge current flows to the inter-electrode gap from the capacitor and the charging voltage of the capacitor decreases. The discharge surface treatment of the treatment target member is performed by repeatedly charging and discharging the capacitor. In the treatment using the capacitor circuit, it is possible to generate a discharge of low discharge energy with a low peak current value and a narrow pulse width by adjusting the electrostatic capacitance of the capacitor, whereby a treated surface having a low surface roughness can be obtained.
On the other hand, Patent Literature 1 discloses an electric discharge machining power supply apparatus that turns on/off a switching element provided between the DC power source and the capacitor in accordance with predetermined pulse trains.